Yes because of your description I figured the Power Supply was not responding "on demand" when Higher requirements are set by the whole system.

I really can not see why you are so stuck with the voltage regulator system!!, I have even thought you may have the LM 317 connected in reverse related to Input-Adjustment legs (The two on sides)...We all know that center is Output, however the basic confusion is at the A and I legs...This transistors are "resettable" they hardly go bad unless fried...by a very high voltage exceeding its max values (36V)
It shouldn't heat up that much (I mean LM317 heat up...it is normal...) unless doing long times at high peaks (full blast)...Do you have it on a Heat Sink?
It also seems like you have not enough Capacitance response in your power supply...meaning, your Electrolytic Caps ain't working right somehow, either are not good, or are connected the wrong way.
The little caps (2.2 and 10 uF) as the 1000 uF are very important to this regulator, makes it more 'robust'...I mean there are only like 6 or seven components total here...
My only mistake in the latest Update was the resistor parallel to diode to be 220 ohms instead of 2.2 K...just the one to ground is 2.2 K...but the rest is identical to mine, and it is working perfect.
So, my only conclusion here is that you, are connecting the LM317 the wrong way...check it out again...slowly...easy...
also check the Caps at the regulator...connections and conditions...
The other thing is...What batteries are you using?..LiPo's?...How many Amps?
The Batteries am using are Fully charged 37 Volts, totaling 6.6 Amps (2200 mA each pack out of three that have around 12V ea)

Good luck...and please do it carefully, I am waiting very enthusiastic to see those Neons bright up your skies there...

Cheers

Ufopolitics.

Hi Ufo,

I have rebuilt the regulator to the latest specifications you have laid out and it works well, works at around 13.7v, I've also used a larger heat sink and temp is not bad.

The only problem is the same thing is happening with the drop off in power to the coil. I have done all the checks with the regulator and it is supplying a constant voltage and amperage without a problem. Supplies to a higher load separate to the circuit as well.

I have measured the voltage to the gate of the mosfets and have found it to be the same as before. Max I can get is just over 5v and quickly drops off to a max of around 2.5v.

The batteries I am using are 3*12v gel cells. I have tested them all individually with 2 halogen bulbs at 70 watts total with no problem.

What do you think could be the problem? Maybe its something to do with one of the components in the 555 circuit.

I can light the neon for a few sec. before it goes out.
I couldn't help connecting a dc motor up to try. It spun it up but as soon as it reached speed the power drops off.